Aluminum tetrabromophtahalate



United States Patent 3,354,191 ALUMINUM TETRABROMOPHTHALATE Edward C.Stivers, Atherton, Califi, assignor to Raychem Corporation, RedwoodCity, Calif., a corporation of California No Drawing. Filed Mar. 27,1963, Ser. No. 268,481 1 Claim. (Cl. 260-448) This application is acontinuation-in-part of my copending application Ser. No. 257,764, filedFeb. 11, 1963, the disclosure of which application is incorporatedherein by reference.

The present invention relates to novel and improved flame retardants.More particularly, the present invention relates to flame retardantscomprising derivatives of halogen-bearing carboxylic acids.

Flame retardant systems which comprise the combination of halogenatedorganic compounds such as highly chlorinated paraflin with an inorganicoxide or salt such as antimony salts have found some use in the priorart. However, the organic components of these systems have been found tobe subject to several serious deficiencies. One such deficiency is theundesirably high water sensitivity of these components.

This water sensitivity is detrimental to the combustion resistance ofconventional flame retardant systems and, in addition, is detrimental tothe dielectric properties of the materials in which conventional flameretardants are often incorporated. The latter disadvantage ofconventional flame retardants is of considerable importance becausethese retardants are often incorporated in polymeric materials which areemployed as electrical insulating materials.

The water sensitivity of conventional flame retardants manifests itselfwhen compositions containing these flame retardants are subjected totreatment with boiling water. Such treatment results in substantial lossin combustion resistance and deterioration of the dielectric propertiesof the composition because of hydrolysis and/or loss of thehalogen-bearing organic or inorganic component of the flame retardantsystem to the water. Furthermore, these systems also manifest theirwater sensitivity when subjected to relatively humid atmospheres andrelatively high temperatures because of hydrolysis of the organiccomponent into fragments which are capable of ionization and hence areelectrically conductive and/ or as a result of sublimation. Furthermore,this fragmentation by hydrolysis often results in the formation ofhighly volatile compositions, thereby decreasing combustion resistance.

Another serious deficiency of conventional flame retardant systems isthe tendency of these systems to volatilize or sublime at elevatedtemperatures which often causes decomposition with resultant liberationof corrosive materials such as hydrogen halides. The present inventionprovides compositions which may be used in flame retardant systems andwhich are not subject to these deficiencies.

It is a principal object of the present invention to providecompositions comprising derivatives of halogen-bearing carboxylic acidswhich derivatives are substantially insoluble, substantially resistantto hydrolysis and which have desirably low volatility andsu'blimab-ility, which compositions are useful in flame retardantsystems.

It is another object of the present invention to provide compositionswhich may be used in flame retardant systems and which will functioneffectively at levels of addition less than those necessary forconventional flame retardants.

Still another object of the present invention is to provide flameretardant compositions which do not substantially impair the physicalproperties, e.g., flexibility,

strength, etc., of the flammable materials into which they areincorporated, and in some cases, actually improve some or all of theseproperties.

A further object of the present invention is to provide compositionswhich may be used in flame retarded systems which are incorporated incross-linked polymeric compositions.

Other objects and advantages of the present invention, it is believed,will be readily apparent from the following detailed description ofpreferred embodiments thereof.

Briefly, the present invention includes within its scope certainderivatives of halogen-bearing carboxylic acids which are useful ascomponents in flame retardant systems. Among these derivatives are metaltetrabromophthalates, metal tetraiodophthalates, metal trihalobenzoates,metal salts of endo-1,4,5,6,7,7-hexach1orobicyclo-(2.2.1)-5-heptene-2,3-dicarboxylic acid (sometimes referred to as HET orchlorendic acid), and metal salts of tetrahalo-o-sulfobenloic acids.

These derivatives may be combined with suitable salts of the inorganicelements in Groups III, IV, and V of the Periodic Table as set forth inthe Handbook of Chemistry and Physics, page 393 (37th ed., 19554956),published by the Chemical Rubber Publishing Company. It is believed thatsalts of these elements combined with the derivatives of the presentinvention at flame temperature to produce an inorganic halide whichvolatilizes and effectively functions to inhibit burning. Examples ofsuch flame inhibiting inorganic halides are antimony trichloride andbismuth tribromide.

The flame retardant derivatives of the present invention may be combinedwith virtually any compatible flammable material, e.g., polymericmaterials, such as polyolefins, polyurethanes, polystyrene, etc.

The present invention is further illustrated by the following examples.

Example I 464 grams of tetrabromophthalic anhydride were treated with115 grams of potassium hydroxide in two liters of water. As this mixturewas gently heated in a beaker, the anhydride reacted and went intosolution. The pH of the resulting mixture was about 8. Five grams oftetrabromophthalate anhydride was added to the reaction mixture so as toadjust the pH to 6. The result was a cloudy solution. The hot solutionwas clarified by filtration and, upon cooling, dipotassium tetrabromophthalate crystallized out. More dipotassium salt could be inducedto separate by the addition of methanol. The resulting slurry wasfiltered and the solid washed several times with methanol and dried inan oven at 110 C.

14.7 grams of calcium chloride dihydrate was dissolved in 100 ml. ofdistilled water. 56 grams of dipotassium tetrabromophthalate wasseparately dissolved in 200 ml. of distilled water. The two solutionswere mixed and an immediate precipitate of calcium tetra'bromophthalateresulted. The precipitate was filtered, washed with hot water, washedwith dilute potassium hydroxide solution dilute hydrochloric acidsolution and, finally, hot water C.) to a pH of 7. It was observed thatsome of the calcium salt dissolved in the hot water, and subsequentlycrystallized out as the filtrate cooled. The calcium salt was trituratedwith boiling methanol and filtered. The product was dried at C. Theyield was about 50% of theoretical.

Example I] 928 grams of tetrabromophthalic anhydride were reacted with230 grams of potassium hydroxide in 5 liters of distilled water. Asubstantial amount of heat was generated by this step and the resultingcloudy solution appeared to be near boiling. The pH of the solution wasabout 6. The solution was filtered to remove traces of undissolvedanhydride and neutral organic matter. 500 grams of aluminum nitratenonahydrate, dissolved in 2 liters of water were added to the clearfiltrate while still Warm. An immediate fine particle size precipitatewas ant systems described in this example are also substantiallynon-volatile and thus are particularly useful in flammable compositionswhich have high curing temperatures such as silicone resins which mustbe cured at temperatures of formed of aluminum tetrabromophthalate. Theprecipitate 5 250 C. and higher. These flame retardant systems are wastriturated with boiling distilled water and filtered. also useful inhigh vacuum applications for the same rea- Finally, it was trituratedwith boiling methanol to remov son. The aluminum salt is particularlyresistant to subt-races of unreacted anhydride and filtered. The yieldwas limation. about 90% of theoretical. No sublimation was observed Thimprovement i th d l f elasticity of the when this product was heated toover 300 C., whereas samples of the present invention comprises asignificant with the anhydride precursor, sublimation occurred atadvantage of this invention. This improvement is a rather 150 C. and, astemperature approached 260 C., sublimamarked departure from conventionalflame retardants tion was appreciable. which have a tendency to impairthe structural properties of polymeric materials. Example It has alsobeen found that the salts of this example are The silver, stannic andzinc tetrabromophthalates were highly ff ti unit Weight For example, thel imade aCCOIdiHg t0 the Process described in Example I num salt appearsto be 70% more effective per unit Weight With the fixceptioh that thenitrates of these metals were than the anhydride. This significantincrease in effectivellsed rather than Calcium llhrateness is believedto be a result of the substantial non-vola- The flame retardantproperties of these materials were tility f the aluminum Salt and,perhaps, the result f tested as follows! possible formation of aluminumhalide at flame tempera- Example IV tures which might itself have aflame retardant action. The following basic formulation, expressed inparts by weight, was used for testing purposes: Example V polyethylene(DYNK) 1() The following basic formulation, expressed in parts byAntimony id 25.0 weight, was prepared for testing purposes: Carbon black(Wilson Masterbatch 3762) 10.0 4,4-thiobis-(o-t-butyl-m-cresol) 1.5Polyethylene (DYNK) 100 Tfiallyl cyamlrate Carbon black (WilsonsMasterbatch No. 3762) 10 Thmbwmolhthalate Salt4,4'-bis-thio-(6-t-butyl-m-cresol) 1.5 DYNK is a polyethylenemanufactured by Union Car- T i u l eyanurate 4 hide and has a meltindexof 0.20.fl. Th s polymer was Antimony oxide 25 combined wlth theremaining mgredlents in this and the following examples by milling on atwo roll laboratory Flame retardant (ground but generally not mmscreened) 30 Slabs comprising this formulation were formed. These slabshad a thickness of 4 inch and were irradiated with Samples were preparedin the same manner as that dehigh energy electrons to a dose of 20megarads. These scribed in Example IV with the exception that some slabsslabs were tested according to the procedures described in 40 were notirradiated and some slabs were irradiated at the footnotes in Table 1.The results of those tests are set doses of 40 mega indicated in Tablewith high forth in Table 1. energy electrons. These samples were testedaccording to TABLE 1 [20 mrad dose] Tctrabromophthalate Flame retard-Sublirnability Heat aging Watersen- Reaction with Modulus, salt ancyaction 1 sitivity 4 boiling water 5 psi. (1500 f psi Tetrabromophthalic-Good Substantial." Flexible 5. 9-3. 5-2.7 52 80 control anhydride.Aluminum Excellent 5. 9-5. 1-4.8 89 107 Fair H 82 73 l. o ..d0 l 71 56Excellent Very slight cracki 5 94 53. 8 54 Fair Cracking 70 Good Verybrittle 102 49 ASTM Test D-635.

2 Strips placed in lightly corked test tubes for hours at 175 C, afterwhich time the surface of the strips was examined for the presence ofwhite sublimate.

3 As (b) above, strips examined for flexibility.

4 Strips suspended over surface of distilled water in lightly corkedtest tube for 120 hours at 90 0., after which time the surface of thestrips examined for "the presence of white product.

Approximately 1 gram of small slivers (cut with razor blade) from theirradiated slabs (20 mrad.) were added to 200 ml. of distilled Water.The pH was measured (the first number). The mixture boiled for 10 min.,cooled and the pH measured (the second number). The mixture was againboiled for 10 min., cooled and the pH measured (the third number).

6 Modulus of Elasticity at C.

the general procedures described in Example IV and the results are setforth in Table 2.

The salts of HET acid and tetrabromo-o-sulfo-benzoic acid used in thisexample were prepared by treating the corresponding anhydride with twomols of potassium hydroxide in an aqueous system and subsequently addingthe corresponding metal nitrates. The synthesis of these salts wasotherwise substantially similar to the procedure brought into contactwith boiling Water. The flame retard- 75 described in Example 1.

TABLE 2 Is flame re- 20 mrad Samples tarding action Basic recipeincluding Flame retard- Was there affected by flame retardant ancyaction 1 dripping? irradiation? Modulus Ultimate Water Heat aging 4 (to40 mrads) at 150 C strength sensitivity 8 (p.s.1.) 2 (p.s.i.)

Cupric tetrabromophthalete.... Self extinguish- No N 49 51 CrystalsBrittle. White ing 0.4 in after 86 sublimate. mm.

Nickelous tetrabromophthal- Drips out Very much No 86 51 Brittle. A veryslight ate. sublimate.

Ce1;ium(HI)tetrabromophthalrio do No 105 100 Slight cracking.

Ferric tetrabromophthalate.--. Self extinguish- Slight No 71 61 Brittle.

ing 0.2" m mm.

Ferrous tetrabromophthalate... Self extinguishdo No 98 96 Do.

ing 0.4" in mm.

Mercuric tetrabromophthalateu Drips out Very much 102 114 White bloomVery flexible. White after 76 hrs. sublimate.

Beryllium tetrabromophthal- Completely Only on 40 No 92 78 None Brittle.A very slight ate. self extinmrad sublimate.

guishing. sample.

Yttrium tetrabromophthalate.- Self extinguish- A function of Yes 94 120.do Very flexible.

ing or drips irradiation out. dose.

Indium tetrabromophthalate... Drips out Very mucb No 72 52 do Do.

Gallium tetrabromophthalate do .do No 61 46 do D0.

Aluminum endo-l,4,5,6,7,7- Self extingmsh- No (slight on No 212 77 Very,very Brittle. Very small hexachlorobieyclo-[2.2.11-- ing 0.9" in 0 madsamslight white amount of white heptene-2,3-dicarboxylate. 1% min bloom.sublimation.

Same as above, but salt Self extinguishd0 No 205 108 None Brittle. Nosublimascreened through 325 mesh ing 0.6 in tlon. screen (a new batch ofsalt). min.

Lead (II) endo-3,4,5,6,7,7- Burns 0.9/min.. N0 No 90 67 do Veryflexible. Very hexachlorobicyclo[2.2.11-5- small trace ofheptene-2,3-dicarboxylate. sublimation.

Aluminum tetraiodophthalate Self extinguish- No No do Do.

ing immediately after flame is taken away.

Barium tetrabromobenzoate- Burns l.4lmin Nn N 0 do Do.

o-sulfonate.

1 ASTM Test D-635.

2 Modulus of Elasticity at 150 C.

B Strips suspended over surface of distilled water in lightly corkedtest tube for 264 hours at 90 C. after which time the surfaces of thestrips were examined for the presence of surface deposits.

Example VI Aluminum 2,3,4-triiodobenzoate was made by neutralizing theparent acid with potassium hydroxide in dilute aqueous solution.Aluminum nitrate was added to this neutralized solution and an immediatewhite precipitate was formed. The product was washed with water to pH 7and dried at 100 C. Two basic formulations, expressed in parts byweight, were prepared for testing purposes as follows:

Formulation Formulation A B.

Polyethylene (DYNK) Antimony oxide Carbon black (Wilsons MasterbatchTriallyl cyanurate Aluminum 2,3,4triiodobenzoate These formulations wereformed into slabs having a thickness of A inch. Some of these slabs wereirradiated with high energy electrons to a dose of megarads. These slabswere then tested according to ASTM Test D-635. The results of thesetests are set forth in Table 3.

TABLE 3 Formulation Irradiation Dose Observation A 0 Immediatelyself-extinguishing after removal of flame.

A 20 Do.

B 0 Self-extinguishing before 1 mark.

B 20 Do.

4 Strips placed in lightly corked test tubes for 264 hours at 175 Cafter which time the strips were examined for the presence of sublimateand examined for flexibility.

Example VII Representative flame retardant systems of the presentinvention were tested with polymers other than polyethylone.Formulations were prepared as follows:

Polystyrene Aluminum endo-l 4,5 6,7,7-hexa- Sample N 0. (parts byweight) chlorobicyclo (2.2.1-5-heptene 2,3

dicarboxalate (parts by weight) 7 8 The formulations were formed intoslabs having a References Cited thickness of A inch and tested accordingto ASTM Test UNITED STATES PATENTS e r T D635. The results of thesetests are indicated in i able 4- 1,990,864 2/1935 Gensel et a1 TABLE 42,103,657 12/1937 Andersen 26013 Average burning rate in inches/ 52,275,211 3/1942 Urbain et a1. 210-24 Sample No.2 min. or classification2,769,731 11/1956 Schneid et a1. 117138.5 1 l.75i0.42. 2,830,079 4/1958Bruce et al. 260-501 2 1.79:0.54. 2,848,470 8/1958 Girard et al. 2604293 Self-extinguishing before 1" mark. 10 3,042,614 7/1962 Halter et al.252--33.6 4 2.18:0.42. 5 Approximately OTHER REFERENCES 6 Approximately1", Beilstein Organische Chemie, Band 9, System Number 7Self-extinguishing before 1" mark, 891-1050, Julius Springer, Berlin(1926), pp. 820-823. 8 Approximately 1" Holderried Paint, Oil andChemical Review, vol. 121

15 Having fully described my invention, it is to be under- (1958) 8stood that I do not Wish to be limited to the details set TOBIAS LEVOWPrimary Examiner forth, but my invention is of the full scope of theappended c1aim HELEN M. MCCARTHY, Exalmmer.

I 20 A. P. DEMERS, Assistant Examiner. Aluminum tetrabromophthalate.

